Over the years the fundamental electric motor construction has been improved in various ways, to facilitate better speed control and/or better operating characteristics, such as smooth operation in a stepping mode with minimum cogging. Other improvements have been made to regulate the speed and/or torque of the motor. One such approach is described in U.S. Pat. No. 4,039,909--Baker, entitled "A Variable Speed Electronic Motor And The Like." This patent describes a system for regulating the amplitude and frequency of the different voltages applied to the stator and to the rotor. As indicated, this is done with slip rings and the motor construction is generally conventional. However, even with such arrangements, there is still a real need for an improved motor in a control system which admits of even more precise control, operation as a stepping motor, and in a manner that does not exhibit cogging.
It is therefore a primary object of the present invention to provide an improved motor and control circuit which provides more precise control of output speed, torque, power factor, and physical displacement of the output shaft than is possible with known devices.
It is a more specific object of the invention to provide such a motor and associated control circuit in which the interacting magnetic fields of the rotor and stator can be "shaped" or regulated to provide different operational characteristics.
In general, an electrical motor can be considered a device for translating electrical energy into mechanical motion. Another important object of the invention is to provide an electrical motor which is functionally reversible. That is, a mechanical motion imposed upon the motor will cause the motor to produce electrical signals for storage, and subsequent playback of such stored signals will recreate the initial mechanical motion of the motor.